Mold for making hollow articles of plastic material



Aug, 5 1924.

F. T. ROBERTS MOLD FOR MAKING HOLLOW ARTICLES OF PLASTIC MATERIAL FiledJuly 9. 1921 ZNZZZNTOZZ 06.4; f flmw All 022%)? THOJH'AS ROBERTS, OF P 5Mom) roe.

l Application filed July 9,

Too whom it may concern:

Be it lmown that I, Faun THoMAs Ronnms', a citizen of the'United States,residing at Philadelphia, in the county of Philadelphia and State ofPennsylvania, have invented a certain new and useful Improvement inMolds for Maki Hollow Articles of'Plastic Material of which thefollowing is a full, clear, and exact description, reference being hadto the accompanyin drawings.

his invention relates to the manufacture of hollow rubber articles andis directed to the improvements in the construction of pneumatic formingmolds of the general tvpe described and illustrated in Letters PatentNo. 1,346,848 issued to me July 20,

1920, for a method 0% making hollow rubber 4 articles.

- accurately superposed. Such forming mold has a raised annular cuttingedge surrounding a cavity and suitable passageways are rovided to enablesuction to exhaust the air cm the cavity and consequently causes acollapse into the mold cavity of. the material from which the articlesare being molded.

The general object of this invention therefore is' the provision of amold member wherein accurac and economy of construction may be at inedby arranging ai plurality of 1 ha g uniform cavities formed. in one endthereof in a mold holder, in er ww re ation.

t e drawings, Fig. 1 represents a plan view of a mold holder, while Fiv2 is a HOLLOW 1.:

men or r'rxc mars a: z.

1921. Serial No. 48$,d0t.

in obtaining-uniformity wlien machining the mold cavities. To form themin the surface of a solid metallic block is an operation m i mar;rmmsvnvn.

both cumbersome and expensive. The formation of accurate raised edges,which serve as severing or parting means for shearing the moldedmaterial around the perimeters of the mold cavities, also requiresconsiderable skill and time. 1

To eliminate these ex nsive operations,

I have provided indivi ual mold blocks 4 having the cavities and cuttingedges and I mount thesein a mold holder 5, which is provided with a backreinforcing plate 6.

This back plate may be secured to the mold holder by any suitable means,suchas screws 7 positioned around the outer edge of the mold member. Amargindl gasket 8 between the holder and plate insures an air tightconnection, while by recessing the lower face of *the holder I provide asuction chamber, as

hereinafter described, and ll'eliminate the necessity; of finishin moreof the lower face of the holder than t e marginal portion.

In making the holder the faces may first V be finished, after which theymay be tem porarily clamped or bolted together, after which spacedopenings, corresponding to the diameter of the individual mold members 435 may then be bored in both the upper and lower mold holders in oneoperation, thus insuring perfect alignment of these bored i The cavitiesin the mold members 4 are particularly adapted to the molding of hollowspherical objects and may be formed in the end of the mold members by asimple turning. operation with a, forming tool, the

cutting edges of which may correspond to at the contour of the cavity tobe formed. A similar tool may be used for forming the severing edgessurrounding the perimeters of the mold cavities. The proper depth of thecavity in such an operation is readily loo obtained. 7

The diameter of the mold members may be only slightly less than thediameter of the bored openings in the mold holder so that the individualmold member may we snug fit these openin with their lower ends seatingfirmly on t e back plate 6.

It is important that the'shearing edges 10 of the mold block be in acommon plane of hollow rubber articles where a number when the molds areassembled in the holder. of the articles are molded simultaneouslyHence, a distinct advantage is obtained by 'derable 'dificulty has beenexperienced h 1|; plate 6 removably seblock to raise it to the properheight. Sufficient rust soon fbrms on the cylindrical surfaces of theblocks to give them a tight fit in the holder.

Suitable vents 11 may be formed'in each mold block to providecommunication between the mold cavity formed in the outer,

end thereof and a transverse slot 12 formed in the bottom surface of themold member. This slot may have a depth corresponding to the thicknessof the gasket 8 interposed between the bottom surface of the mold holder5 and the inner surface of the sup-- porting plate 6. I v

The gasket member 8 thus serves as. a spacing member to provide asuction chamher 14 between the mold holder and the plate aswell as aseal therefor. Suitable open ings 15 communicating with a couplingmember 16 secured to the side of the mold holder may providecommunication between the exhaust chamber 14 and an exhaust tube 17connected to suction means, not shown.

I thus obtain a very simple and economical arrangement of the exhaustvents and connections with the suction machine.

An annular groove 18 formed in the upper face of the mold holder mayhave suitable vent openin s 19 communicating with I the exhaust cham er1 1 so that when a sheet of material is placed over the surface of themold, the edges thereof may be drawn into the grooves 18. A seal betweenthe under surface of the sheet and the upper surface of the mold holdermay thus be obtained.

Similar vents 20, extending from the upper surface of the mold holder'to the exhaust chamber, serve as outlets for exhausting the spacebetween the upper surface of the mold holder and the sheet of materialto be molded.

d claim:

1. A mold of the class described, comprised substantially of a moldholder having abase late and a series of individual cy- 5 lindrica moldmembers having mold cavities in one end thereof and having projectingedges surrounding the cavities, said members being seated in cylindricalopenings in the mold holder and having their extreme ends opposite thecavitary ends engaging the base plate, whereby adjustment of theindividual members may be made to osition said edges at a common heightrom the base of the mold holder. w 2. A mold of the class described com-Having thus described my invention, I,

mosses prised substantially of a mold holder provided with an exhaustchamber and a plurality of separately formed mold members carried by theholder having mold cavities formed therein, and having communicatingpassageways between said cavities and the exhaust chamber in the holder,whereby the air in said cavities may be exhausted.

3. A mold. of the class described comprised substantially of a moldholder provided with an exhaust chamber, and a plurality of individualseparately formed mold members mounted in the mold holder and havingcavities, said mold holder having an annular groove formed in the uppersurface thereof and passageways providing communication between thegroove and the exhaust chamber, whereby the ends of a sheet of materialplaced over the mold members may be drawn into the groove when air isexhausted from said exhaust chamber.

4. A mold of the class described comprised substantially of a moldholder and a series of individual separately formed members mounted inthe holder and having projecting edges surrounding mold cavities formedtherein, there being communicating passageways between said cavities andan exhaust chamber in the holder, whereby the air in said cavities maybe exhausted.

5. A mold of the class described comprised substantially of a moldholder provided with an exhaust chamber, and a plurality of mold membersmounted in the mold holder and having each a mold cavity in its end anda raised severing edge surrounding the cavity, said mold holder havingan annular groove formed in the upper surface thereof, and passagewaysproviding communication between the groove and the exhaust chamber,whereby the ends of a sheet of material placed over the severing edgesof the mold members may bedrawn into the groove when air is exhaustedfrom said exhaust chamber. 6. In a mold of the class described, thecombination of a mold hdlder having a pluralit of openings formedtherein,-a supporting plate secured to the underside of the mold holder,the walls of said openings extending at right angles to the supportingplate, and a plurality of cavitary mold members having their sidesurfaces extending continuously at right angles to said supporting plateand positioned in said mold holder openings and having the ends oppositethe cavity resting on said supporting plate."

7. In a mold of the class described, the

combination of a mold holder having a pluralityof uniform openingsformed therein, a supporting plate secured to the underside of the moldholder, a gasket interposed therebetween, and a pluralit positioned insaid mold older openings and adapted to rest on said supporting p ate.

of mold members and a pluralitv of molding blocks rality .counication isestablished of the mold holder, a gasket interposed between the moldholder and supportmiplate,

se cavities form in the upper ends thereof 0- sitioned in the open' ofsaid-mold hol er, said mold blocks having vent openings extending fromsaid upper mold cavities downwardly and adapted to communicate with thespace between the mold holder and the supporting. late.

9. A mol of the class described comprised substantially of a mold holderhaving a plu of openings formed therein, a support plate secured to theunder surface of the m d holder, a gasket interposed between the moldholder and supporting plate, and a plurality of mol blocks havingcavities formed in the upper ends thereof ositioned in the openings ofsaid mold ho der, said mold blocks having vent openingis extending fromsaid upper mold cavities wnwardly and terminat .in grooves formed'in theunder surface of the mold blocks, whereby tween the mold cavities andthe space between the mold holder and the supp plate.

10. in a mold of. the case described, the combination of a mold holderha i l haust chamber formed therein, 03 a rality of separately formedmoldmem rs,

supported by the mold holder in such a manner that the upper ends of themold members may project a uniform distance from the upper surface ofthe mold holder, andthe lower ends of the mold. members may project auniform distance into. said exhaust chamberfwhereb a assageway extenthrough the mold mem ers may provide communication from mold cavitiesformed in t upper ends of the mold members to said exhaust chamber.

11. En-a mold of the class describwflzhe combination of a mold holderand a plurali of mold members eged in the mold cavities formed in theupper. ends thereof, the mold members ha projecting edges of uniform heiht surrounding the cavities, and the mold member being provided withpassageways ending from the spaces intermediate said projecting edgesand said exhaust chamber whereby a sheet of material placed upon saidprojecting edges may drawn into contact with the upper surface of themold holder. 1

plurality of. cydindrical mold members occup the re and supported on thefrom said base of the holder, said mold members having projecting edgessurrounding mold cavitiesformed in the upper surfaces thereof,

and being adjustable in the mold holder whereby said edges may bepositioned at a uniform level.

13. A mold block comprising a body having a cupped end surrounded by aprojecting edge, a groove in the end of the mold I block opposite thecutting edges, and a passageway afiording communication between thegroove and the cavity. I

' 14 In a mold block, a cylindrical body portion having a cavity in itsupper end and having a circumferential perip eral cutting portionadjacent the cavity, a groove in the end of saidmold block opposite saidcavity,

and a passageway leading from'said groove to, the mold cavity.

15. In a mold of the class described, the

combination of a mold holder having means thereon for receiving andpositioning mold members, separately formed mold members arranged in themold holder, said mold members having grooves therein whereby the holderserves to support the molds and to provide a vacuum chamber.

16. In a mold of theclass described, a mold holder having a plurality ofpartition portions defining a plurality of independent compartments,mold members arra said comrtments, and communicati pas sageways in themold members and across the partition portions.

'17. The combination, with a holder having a set of cylindrical holestherein, of mold blocks in the respective holes, mob comprising acylindrical body portion snugly. engaging the surrounding portion! of ithe holder and having a cavity in its upper end and havingacircumferentialperipheral cutting portion adjacent the cavity, a groovein the other end of mid mold block opposite said cavity, and a passaeway lea-i1 cove to the-mo d cavity, the holder havi a bottom platewhich the bottoms of said blocks abu I v 18. The combination of' a moldholder having a plurality of spaced compartments, cavitary mold membersarran 1n SdldIBOJlIP partments, and passageways across the space betweenthe compartments arranged to communicate with the cavities in the mold Imembers in the compartments. I 19. The combination of a mold holder.havingla plurality of-spaced compents,

mold bloc v 20. A mold holder "3% a pity of eoaeee openings through it,a plurality of mold' plate extending across the bottom of the 15 blocksoccupying the openings and each havmold member and engaging the blocks,there ing a recess in one end, a supporting plate being passagewaysleading from the cavi extending across the bottom of the mold ties ofthe different blocks throu h the 5 member and blocks, passagewaysleading blocks and. terminating in grooves a jacent from the cavities ofthe difierent blocks, and the supporting plate and there'being space 20means associated with the holder for enabetween the supporting plate andthe parbling the passageways of the different titioning portions of theholder for enabling blocks to communicate with each other. thepassageways of the different blocks to 10 4 21. A mold holder having aplurality of communicate with a common chamber.

openings through it, a plurality of mold In testimony whereof, Ihereunto aflix my 22; blocks occupying the openings and eachhavsignature.

ing a recess in one end surrounded by an a annular cutting edge, and asupporting FD THOMAS ROBERTS.

